Hydraulic method and apparatus for dispensing granular material under pressure



W. L. KING ETAL HYDRAULIC METHOD AND APPARATUS FOR DISPENSING GRANULARMATERIAL UNDER PRESSURE 2 Sheets-Sheet 1 June 2, 1970 Filed July 5, 1967F|G I 32 52 32b @12 4.6! I 1 48 Q 36 2s 30 it:

JOHN F KING WILLIAM mum;

LOYAL W. JAMES /NVFNTORS BUCKHOR/V, BLORE, KLAROU/ST 8 SPAR/(MANATTORNEYS June 2, 1970 w. L. KING ETAL 3,514,905

HYDRAULIC METHOD AND APPARATUS FOR DISPENSING GRANULAR MATERIAL UNDERPRESSURE Filed July 5, 196'? 2 Sheets-Sheet :3

JOHN F KING WILLIAM L. KING LOYAL W JAMES INVENTORS.

United States Patent 3,514,905 HYDRAULIC METHOD AND APPARATUS FORDISPENSING GRANULAR MATERIAL UNDER PRESSURE William L. King, John F.King, and Loyal W. James, Eugene, Oreg., assignors, by mesneassignments, to McKenzie Pump Corporation, Springfield, Oreg., acorporation of Oregon Filed July 3, 1967, Ser. No. 650,932 Int. Cl. B24c3/00 US. Cl. 5112 14 Claims ABSTRACT OF THE DISCLOSURE The apparatusdescribed herein includes a tank for storing a liquid and a granularmaterial, such as water and sand, under an internal hydraulic pressure.A pipeline extends from a liquid pump to an outlet having a nozzle foremitting a stream of liquid under pressure. The pipeline downstream fromthe pump includes first branch line including a perforate pipe sectionextending generally horizontally within the tank and below the upperlevel of granular material within the tank. The pipeline includes asecond branch line in parallel with the first branch line so that aportion of the flow from the pump can bypass the tank. Flow controlvalves are provided in both branch lines for regulating the proportionof total flow through each branch and thereby the concentration of gritin the flow at the nozzle. The tank is provided with a top filleropening for adding granular material and a closable air vent to permitfilling the tank with liquid at line pressure.

As liquid flows from the pump through the perforate pipe section withthe tank under an internal hydraulic pressure approximating the linepressure, granules from the tank pass through the perforations in theperforate pipe section and become entrained in the flow, which carriesthem to the nozzle where they are discharged in a high pressure liquidspray.

BACKGROUND OF THE INVENTION (A) Field of the invention This inventionrelates to hydraudic grit dispensing apparatus, such as, for example,hydraulic sandblasting equipment, used for cleaning and removing paintfrom objects and for etching.

(B) Description of the prior art In prior hydraulic sandblastingequipment and related hydraulic grit dispensing apparatus a venturi orjet spray principle has been utilized most commonly to mix the grittymaterial with a flow of liquid to be sprayed. For example, Umbricht etal., US. Pat. 3,150,467 illustrates the use of a jet spray device andMoore US. Pat. 3,267,615 illustrates the use of a venturi device forthis purpose. However, both types of equipment are relatively complex,expensive, inflexible, and difficult to control. A further disadvantageof a venturi device is that it is subject to 3,514,905 Patented June 2,1970 SUMMARY OF THE INVENTION The apparatus of the present inventionovercomes the problems of expense, complexity, wear, and lack offlexibility of the prior art in that it comprises a liquid pressuresystem including simply a pressure vessel and a pipeline having aperforate pipe section extending within the vessel through which liquidis pumped to a discharge nozzle downstream from the vessel. When thevessel is filled with liquid under a hydraulic pressure approximatingline pressure and at least partially filled with the granular materialto be dispensed, flow through the perforate pipe section,

which may be of constant diameter throughout its length, will inducegranules within the vessel -to enter the fiow, which carries thegranules to the .nozzle where they are dispensed in a liquid spray. Theconcentration of grit in the flow can be varied by varying the rate offlow or the size of the perforations, or by diverting a variable portionof the flow so that it bypasses the perforate pipe section.

BRIEF DESCRIPTION OF THE DRAWINGS i The foregoing and other objects andadvantages of the present invention will become more apparent from thefollowing detailed description which proceeds with reference to theaccompanying drawings wherein:

DETAILED DESCRIPTION FIG. 1 embodiment With reference to the drawings,FIG. 1 illustrates one form of apparatus in accordance with theinvention, including a generally cylindrical pressure vessel 10 having aflat bottom 12 and an open top closed by a cover 14. The cover issecured to an annular flange 16 of the vessel by bolts 18. A gasket 20positioned between the lid and the flange provides a pressure tightseal. The cover has a filler opening 22 through which the vessel may befilled with a granular material such as the sand 24 shown within thevessel. The filler opening is normally closed during operation of theapparatus by a screw type filler cap 26. An air vent pipe 28 extendsthrough another opening in the cover and is closable by a manuallyoperated valve 30.

The apparatus also includes a liquid pressure system including apressure liquid passage means extending from a source of liquid underpressure to an outlet opening. The passage means includes a pipelineindicated generally at 32 connected at one end to a liquid pump 34 andat the other end to a nozzle 36 at the outlet. The pipeline includes aprimary pipe section 32a extending from the pump to a T coupling 38 justupstream from the vessel. At this coupling the pipeline diverges intotwo branch pipe sections, one 32b extending horizontally above thevessel to bypass the same, and the other 320 passing verticallydownwardly through an opening 40 in the cover and into the vessel.Branch section 320 terminates near the bottom of the vessel at a elbow42 to which iscOnnected a perforate pipe section 44, which extends fromone side of the tank to an opposite side thereof just above bottom 12,finally terminating at another 90 elbow 46. A vertical pipe section 32dextends upwardly from elbow 46 and through cover 14 to another Tcoupling 48. Coupling 48 is also the downstream terminus of branch pipesection"32b'."Frorn T 48, the How through both branches merges and flowsdownstream through a common outlet pipe section 32e, which is coupled at50 to a length of flexible hose 52 having nozzle 36 at its outlet end.

Branch pipe section 32b bypassing the tank includes a manually operableregulating and shut off valve 54. A second manually operable regulatingvalve 56 is provided in branch line 32c leading into the tank to theperforate pipe section 44. These two valves are used to regulate andvary the flow through each of the two branches. In fact, the valves canbe used to send all of the flow through either one of the branches, ifdesired.

OPERATION To operate the apparatus of FIG. 1, filler cap 26 is removedand the vessel is at least partially filled with sand or some otherdesired granular material, depending on the end use to which theappaartus is to be put. Then the filler cap is replaced. Valve 30 on thevent pipe is opened, valve 54 closed and valve 56 opened so that thefull flow initially passes through perforate pipe section 44 and intothe vessel. Nozzle 36 is also preferably closed so that the vessel fillsrapidly with liquid flowing through the perforations 58 in pipe section44. After the vessel is filled with liquid, valve 30 is closed so thatthe internal hydraulic pressure of the vessel approximates that of theline. Valves 54 and 56 are adjusted so that the desired proportion ofthe total flow passes through perforate pipe section 44. Thereafter,upon continued flow through branch 32c and the perforate pipe section,granular material flows from the vessel, through the perforations andinto the flow, where it becomes entrained to be carried to the nozzle.At T 48 the grit-carrying flow is merged with any additional flow frombypass line 32b- Under static hydraulic conditions pressure within theperforate pipe section and within the vessel would be equal. However, asliquid flows through the perforate pipe section to the nozzle, a slightpressure differential is created at the perforations due to the flowthrough the perforate pipe section. It is believed that the slightpressure reduction within the pipe coupled with the force of gravityacting on the sand causes the sand to gravitate toward and into theperforate section. A very satisfactory intermixing occurs within theperforate section despite the absence of any venturi or jet device. Thegrit entraining action continues until the level of granular materialwithin the vessel approches the bottom thereof. The concentration ofsand or other grit in the spray is controlled by varying the proportionof fiow through the perforate pipe section, the greater the proportionof the total fiow through the perforate pipe section, the higher theconcentration of grit in the total flow at the nozzle.

The concentration of grit in the final spray can also be controlled byvarying the size of perforations 58 in the perforate pipe section. Thelarger the perforations, the greater will be the rate of flow ofgranules into the perforate pipe section. However, it has been foundthat, in general and depending on the size of the granules, the tendencyof the perforate pipe to clog is increase with an increase in the sizeof the perforations beyond certain limits.

EXAMPLE For example, in one test device made in accordance 'with theembodiment of FIG. 1 and operated with ordinary sand, the perforate pipesection had a three-quarter inch inside diameter with perforationsspaced throughout the circumference of the perofrate pipe section. Itwas found that the apparatus worked best with perforations ranging insize from one-sixteenth inch to one-quarter inch in diameter. Theaforesaid test apparatus was operated with a pump deliverying water atits outlet under pressure of 450 p.s.i. at twenty gallons per minute(g.p.m.). Pipe having a three-quarter inch inside diameter was usedthroughout the system with a hose of one-half inch inside diameter and athree-sixteenths inch nozzle. The vessel itself had an inside diameterof twelve inches and an inside height of eighteen inches. The outletorifice of the pump had a one-half inch inside diameter. With bothvalves 54 and 56 wide open, the apparatus delivered a spray at thenozzle having a concentration of approximately 2% sand, by weight.

FIGS. 2 and 3 embodiment FIGS. 2 and 3 illustrate another, commercialform of the apparatus including a high strength steel tank 180 havingcurved upper and lower ends 102 and 104, respectively, with a filleropening 106 and filler cap 108 at the upper end and a drain opening 110and drain cap 112 at the lower end. The upper end also includes aclosable air vent pipe 114.

In this embodiment a straight perforate pipe section 116 is connected atits opposite ends to axially aligned externally threaded sleeve couplers118, 120 at opposite sides of the tank near the bottom.

More specifically with reference to FIG. 3, couplings 118, 120 arethreaded into bosses 121, 122, respectively, welded to the outside ofthe tank surrounding axially aligned openings 123, 124 therein. Coupling120 is internally threaded to receive an externally threaded end 125 ofperforate pipe 116. The opposite coupling 118 has a smooth but slightlytapered bore at 126 which snugly receives a complementary, tapered end127 of perforate pipe 116.

An inlet pipe section 130 is connected as by welding at its downstreamend to coupling 120 and is connected at its upstream end to a pump (notshown). An outlet pipe section 132 is connected at its upstream end tocoupling 118 on the tank, and at its downstream end to a flexible hoseas shown in the FIG. 1 embodiment.

A branch pipe section 134, which is imperforate and corresponds to thebranch section 32b of FIG. 1, also passes through the tank, bypassingperforate section 116. In fact, the greater length 136 of branch line134 is a single length of pipe welded to opposite sides of the tank. Theopposite ends of pipe 136 are threaded and project outside the tank sothat they can be coupled to the remaining portions of the branch 134 bysuitable couplings. Bypass section 134 is connected to the main inletand outlet pipes 130 and 132 at T connections 138 and 139, respectively.Both the bypass branch 134 and the branch including perforate pipesection 116 are provided with regulating valves 140 142, respectively,outside the tank to control the flow rate through both branches. Anothervalve 144 is provided downstream from the perforate pipe 116 butupstream from T 139 to prevent the drawing of sand into outlet 132 whena gritless flow of fresh water through bypass 134 is desired.

The operation of the tank of FIG. 2 is the same as that described withrespect to FIG. 1.

As one example of the commercial form shown in FIG. 2, the tank has athirty gallon capacity with a sixteen inch outside diameter and a thirtyinch height throughout its cylindrical extent. The tank is made of steeland is capable of withstanding a working pressure of 600 p.s.i. Thefiller opening has a three inch diameter, and the drain opening has atwo inch diameter. All piping, including the perforate pipe section, isthree-quarter inch stock. The openings in the perforate pipe section areof threesixteenths inch diameter and spaced apart longitudinally onthree-quarter inch centers. There are four rows of openings spacedcircumferentially about the pipe, with the holes of adjacent rows beingstaggered with respect to one another.

It is to be understood that the foregoing examples are illustrative onlyand not intended as limitations on the invention except as they may beincluded in the claims. The perforate pipe sections are of constantdiameter throughout their lengths, although this is not essential, thesignificance being that the apparatus does not need to depend on anyventuri action to induce the sand to enter the perforate pipe section.Although the perforate pipe sections in the two illustrated embodimentsextend horizontally, it should be understood that such pipe sectionscould extend at a slight inclination to the horizontal so long as theyparalleled approximately the bottom of the tank. In this regard agenerally horizontally disposed perforate pipe section is much preferredto a generally upright perforate pipe section. The latter woulddrastically reduce the efficiency of the apparatus because as the levelof sand within the tank lowered, it would expose progressively moreperforations above the sand and thereby reduce progressively theconcentration of sand in the spray during any single blasting operation.Continual adjustment and frequent refilling would be required to correctthe situation.

FIG. 4 EMBODIMENT Although the embodiments of FIGS. 1 and 2 show the useof only a single perforated pipe section, it should be understood thatif a higher concentration of grit in the spray is desired than could beobtained with a single perforate pipe section, several perforate pipesections could be placed in parallel with each other within the tank,with the flow through each of the parallel pipe sections eventuallybeing merged at a common outlet pipe section. For example, FIG. 4illustrates somewhat schematically a pressurized tank 150 similar tothat of FIG. 2 partially filled with sand or-other cleansing agent andwater. A pipe 152 leading from a pump (not shown) divides at 153, into apair of parallel pipes 154, 155 which then extend into tank 150. Theparallel pipes include perforate pipe sections 156, 157 within the tank.Parallel pipes 154, 155 then extend outwardly through the tank and mergeagain at 158 into a single outlet pipe 160 which leads to a nozzle orother outlet opening.

The apparatus as described would be used most commonly with sand andwater. However it will be understood that any liquid and granularmaterial could be used successfully in the apparatus of the presentinvention. For example, the apparatus has been used successfully withsawdust in the tank, using water as the carrier. Thus, it is notnecessary that the granular material be heavier than the liquid carrier,although such is preferred for optimum performance. In fact, materialssoluble in water, such as detergents, have been used successfully in thetank, and it is believed that the apparatus could also be used todispense a mixture of two dissimilar liquids, one, such as water, as thecarrier, and another, such as an insecticide, as the material to bedispensed from the tank. However, the apparatus is primarily intendedfor use in dispensing granular material in a high liquid pressure blastfor cleaning purposes.

A particular advantage of the FIG. 2 form is that if a perforate pipesection having larger openings is desired, one perforate pipe sectioncan be replaced easily and quickly by another having openings of thedesired size.

METHOD Summarizing the method of the present invention, it contemplatesthe flow of a continuous stream of liquid carrier through an internallypressurized tank filled with both a mixture of granular material,preferably having a greater density than the liquid, and more of theliquid under pressure approximating the pressure of the stream exceptfor the slightly reduced pressure of the stream due to its velocity. Thestream flow within the tank passes beneath but adjacent to the granularmaterial and is separated therefrom by a foraminous boundary layer whichcontrols the rate of entrainment of granular material in the stream.

Having illustrated and described three preferred embodiments of theinvention, it should be apparent to those having skill in the art thatthe same permits of modification in arrangement and detail. We claim asour invention all such modifications as come within the spirit and scopeof the following claims:

1. A dispensing apparatus including a closed vessel containing a fluentnongaseous material and a pipeline extending from a source ofpressurized liquid carrier through said vessel to an outlet opening,characterized by said vessel being fluid pressure tight and under aninternal liquid pressure when the apparatus is in operation, and saidpipeline including a perforate pipe section extending within an interiorportion of said vessel containing said fluent material, said perforatesection providing a liquid flow path of substantially constant crosssectional area throughout the length thereof and through said fluentmaterial so that the normal flow of said liquid carrier through saidperforate section in flowing continuously from said source to saidoutlet entrains some of said fluent material in said liquid and carriesthe same to said outlet.

2. Hydraulic grit-dispensing apparatus comprising:

a vessel including means for internally pressurizing said vessel,

said vessel including means for adding a granular material thereto,

a liquid pressure system including continuous passage means extendingfrom a source of liquid under pressure to an outlet,

said passage means including a perforate pipe section extendinggenerally horizontally within a lower portion of said vessel downstreamfrom said source and upstream from said outlet, whereby with said vesselat least partially filled with granular material and with liquid, theflow ofliquid through said perforate pipe section induces the flow ofgranules from said vessel into said section Where they become entrainedin flowing liquid and carried therein to said outlet.

3. Apparatus according to claim 2 wherein said perforate pipe section isof substantially constant inside diameter throughout the length thereofwhereby there is a substantial abence of venturi action inducing theentraining of granules in the flow within said section.

4. Apparatus according to claim 2 wherein said vessel includes aselectively closable air vent which permits when open the filling ofsaid vessel with liquid from said perforate pipe section and which whenclosed places the vessel under a pressure approximating the pressure ofthe flow within said perforate pipe section.

5. Apparatus according to claim 2 wherein said passage means includes animperforate branch pipe section in parallel with said perforate sectionso that a portion of the flow through said passage means bypasses saidperforate pipe section, said passage means including a passage sectiondownstream from said perforate and branch pipe sections rejoining theflows from said branch and perforate pipe sections upstream from saidoutlet.

6. Apparatus according to claim 5 wherein said passage means includesmeans for regulating the proportion of the total liquid flow passingthrough said perforate and branch pipe sections.

7. Apparatus according to claim 6 wherein said means for regulating flowincludes a first valve means in said branch pipe section and a secondvalve means in a pipe section in parallel with said branch pipe sectionand connected to said perforate pipe section.

8. Apparatus according to claim 2 wherein said perforate pipe sectionextends through said vessel from one side thereof to another and whereinsaid apparatus includes means for fastening said perforate section tosaid vessel at said sides thereof.

9. Apparatus according to claim 8 wherein said perforate pipe section isthreaded at its opposite ends and said vessel includes threaded portionsat opposite sides thereof for receiving the threaded portions of saidperforate section.

10. Apparatus according to claim 2 wherein said vessel comprises a fluidpressure-tight tank having a greater height than-width and having aclosable filler opening at the top thereof for placing granular materialwithin said tank, and a closable air vent means at the top thereof forpermitting the escape of air from said tank to permit filling of thesame with liquid from said perforate pipe section, and a drain openingat the bottom of said tank,

said passage means comprising a branch passage section branching fromthe primary passage means upstream from said perforate pipe section andrejoining said primary passage means downstream from said perforate pipesection whereby a portion of the flow through said passage meansbypasses said perforate section, valve means in conjunction with saidbranch section and said perforate pipe section for regulating theproportion of the total flow passing through said branch and perforatepipe sections,

said source of pressure fluid including a pump upstream from saidperforate and branch pipe sections, a nozzle at the outlet of saidpassage means, a granular material at least partially filling said tank,a liquid of less density than said, granular material within said tankand under a pressure corresponding to the liquid pressures Within saidliquid pressure system, perforations in said perforate pipe sectionhaving greater diameters than the granules within said tank,

said perforations being arranged throughout the circumference andthroughout the greater portion of the length of said perforate pipesection within said tank.

11. A method of dispensing gritty material in a liquid stream forcleansing and other purposes comprising the steps:

placing a quantity of said gritty material within a pressure-tightenclosure,

filling said enclosure with liquid,

directing a flow of said liquid under pressure from a source outsidesaid enclosure along a flow path of substantially constant cross sectionthrough and in communication with said gritty material and thence to apoint of dispensing outside said enclosure,

and during said flow maintaining said enclosure under a liquid pressureapproximating the pressure of said flow through said enclosure.

-12. A method according to claim 11 including the step:

during said flow separating said flow path from the gritty materialwithin said enclosure with a forarninous material having foramina largerthan individual particles of said gritty material so as to control therate of entrainment of said material in said flow.

13. A method according to claim 11 wherein said liquid flow path isdirected through said gritty material in a direction providing asubstantially constant liquid pressure head acting on said flow pathwithin said enclosure.

14. Apparatus according to claim 1 wherein said perforate pipe sectionextends at a generally horizontal disposition through said fluentmaterial and is provided with perforations throughout substantially theentire horizontal extent of said fluent material within said vessel.

References Cited UNITED STATES PATENTS 709,448 9/ 1902 Shaver 5112847,269 3/ 1907 Wise 51-12 864,471 8/1907 Kelly 51-12 1,727,027 9/ 1929Dreisbach 518 2,076,414 4/1937 Panagopoulos 518 X 2,200,587 5/1940Tirrell 51-321 X 2,573,917 11/1951 Luce. 3,084,484 4/ 1963 Hall et al.51-8 LESTER M. SWINGLE, Primary Examiner US. Cl. X.R. 30216

